Ontogeny of the immune system in Xenopus

Abstract. The larvae and adults of genetically identical clones of Xenopus each produce different populations of antibodies to dinitrophenylated keyhole-limpet hemocyanin (DNP-KLH) upon immunization. The larvae and adults differed with regard to the affinity of their IgM antibodies and the isoelectric-focusing pattern of their low-molecular-weight-Ig (IgG equivalent) antibodies. The larval antibody repertoire for DNP was not changed by the addition of adult helper T cells. Thus, the expression of a larval repertoire is the result of a B-cell pool peculiar to larvae and is not influenced, except in its quantity, by adult T cells.     

Drosophila adult and larval pheromones modulate larval food choice

Insects use chemosensory cues to feed and mate. In Drosophila, the effect of pheromones has been extensively investigated in adults, but rarely in larvae. The colonization of natural food sources by Drosophila buzzatii and Drosophila simulans species may depend on species-specific chemical cues left in the food by larvae and adults. We identified such chemicals in both species and measured their influence on larval food preference and puparation behaviour. We also tested compounds that varied between these species: (i) two larval volatile compounds: hydroxy-3-butanone-2 and phenol (predominant in D. simulans and D. buzzatii, respectively), and (ii) adult cuticular hydrocarbons (CHs). Drosophila buzzatii larvae were rapidly attracted to non-CH adult conspecific cues, whereas D. simulans larvae were strongly repulsed by CHs of the two species and also by phenol. Larval cues from both species generally reduced larval attraction and pupariation on food, which was generally—but not always—low, and rarely reflected larval response. As these larval and adult pheromones specifically influence larval food search and the choice of a pupariation site, they may greatly affect the dispersion and survival of Drosophila species in nature.     

Relationship between adult and larval host plant selection and larval performance in the generalist moth, Trichoplusia ni

Adult oviposition preferences are expected to correlate with host plant suitability for the development of their offspring. For most lepidopteran species, this is particularly important as the hatching neonate larvae of many species are relatively immobile. Thus, the site of oviposition chosen by a female adult can greatly influence the probability of survival for her offspring. In the present study, we investigated the oviposition preference of adult Trichoplusia ni moths for six plant species to determine whether they could accurately rank the suitability of the plants for larval development. We also compared oviposition preferences to neonate larval acceptance and preference to determine whether the adult host range matched that of larval diet breath. Our results indicate that in two-choice and no-choice tests adult T. ni were able to rank the plants accurately, with the exception of anise hyssop. However, when given a choice of all six plants together, they laid more eggs on a plant that was not suitable for larval survival. Larvae accepted and fed on all plants in no-choice tests, and accurately ranked them according to larval performance. We conclude that neonate larvae are better able than adults to rank plants according to larval performance, and that larval diet breadth is wider than the range of plants accepted by adults. We also provide a discussion of the reduced accuracy of adult oviposition preference with increased plant choices.     

The consequences of egg cannibalism inAdalia bipunctata [Coleoptera: Coccinellidae]

When eggs ofAdalia bipunctata L. are offered to larvae of their own species, these larvae are able to develop to adults. Reducing the daily egg supply results in decreased larval survival and pupal weight and especially fecundity of the adult females. The duration of larval development is significantly increased, the longevity of adults is shortened.     

Susceptibility of larval Crepidula fornicata to predation by suspension-feeding adults

The slipper shell snail Crepidula fornicata forms dense assemblages along much of the European coast, where it co-occurs with oysters. We examined the susceptibility of slipper shell larvae to predation by suspension-feeders, including adults of their own species. In particular, we compared filtration rates on phytoplankton with those on larvae, and determined the extent to which consumption of larvae varied with adult size, larval size, and with the presence of alternative food (phytoplankton). We also examined the ability of competent larvae to metamorphose successfully in the presence of feeding adults. For each experiment, adults were held in plastic jars with seawater or phytoplankton suspension and allowed to graze on larvae (101 larvae per jar) for 4-6 h at room temperature (21-23 °C); larvae were kept in circulation with gentle aeration. Adults of C. fornicata ingested substantial numbers of larvae over the complete range of sizes tested, about 450-850 μm shell length. Ingestion rates were reduced by 43-50% in the presence of phytoplankton, and were not correlated with adult shell length. The rates at which larvae were removed by adult slipper shells were generally lower than predicted from the rates at which the same adults ingested phytoplankton, suggesting either some ability of larvae to avoid capture or some difficulty of adults in consuming larvae entrained into their feeding currents. Slipper shell larvae were also readily consumed by adult oysters (Ostrea edulis and Crassostrea gigas), and indeed oysters consumed larvae at faster rates than predicted from their phytoplankton ingestion rates. Nevertheless, substantial numbers of competent larvae managed to metamorphose successfully during the test periods, either on the sides of the jars they were in or on the adults' shells, suggesting that recruitment probably continues in the field even when suspension-feeding adults are at high concentrations in the benthos.     

Interactions between adult and larval bluegill sunfish: positive and negative effects

Adult fish may affect the growth and survival of conspecific larvae through a variety of pathways, including negative interactions via competition for shared limiting resources or via predation (i.e., cannibalism), and positive interactions due to the consumption of larval predators and via resource enhancement (i.e., presence of adults increases availability of larval prey). To examine the overall effect of adult bluegill sunfish (Lepomis macrochirus) on larval bluegill, we conducted a field experiment in which we manipulated adult densities and quantified larval growth and survival, prey abundance, invertebrate predator abundance, and cannibalism. The presence of adult bluegill had a negative effect on final larval mass. This response was consistent with competition for zooplankton prey. Adult bluegill reduced the abundance of large zooplankton (e.g., Chaoborus and Daphnia), which were the dominant prey of bluegill larvae in the absence of adults. Larvae in the no-adult treatment also had significantly more prey in their stomachs compared to larvae in the presence of adults. Larval survival was maximized at intermediate adult densities and the overall production of larvae peaked at intermediate adult densities. The higher larval survival at intermediate adult densities is attributed to a reduction in invertebrate predators in treatments with adult bluegill; invertebrate predators experienced an 80% reduction in the presence of adult fish. Decreased larval survival at the highest adult density was not due to resource limitation and may be due to cannibalism, which was not directly observed in our study, but has been observed in other studies.     

An improved method to obtain antigen-excreting Toxocara canis larvae

Toxocara canis is a dog helminth which causes visceral larva migrans (VLM) when infecting humans as a larva. The infection is demonstrated by detecting IgG antibodies against excretory-secretory larval antigens (ESLA) in serum by ELISA. The production of ESLA involves the collection of adult worms from dog puppy stools, the separation of eggs from dissected uteri, and the in vitro growing of egg-derived larvae, following the time-consuming and laborious protocol described by De Savigny [De Savigny, D.H., 1975. In vitro maintenance of T. canis larvae and a simple method for the production of Toxocara ES antigen for the uses in serodiagnostic tests for visceral larva migrans. Journal of Parasitology 61, 781-782]. In this work, an improved protocol for obtaining T. canis larvae is described. The modifications proposed improved the efficiency of the original De Savigny method in three ways: (i) increasing the parasite yield up to five fold, (ii) improving the larval purity, and (iii) markedly reducing the execution time of the protocol.     

Larval settlement and metamorphosis in the slipper limpet Crepidula onyx (Sowerby) in response to conspecific cues and the cues from biofilm

In the marine environment, aggregated distribution in the genus Crepidula is a very common phenomenon. Works from Pechenik's group suggested that this is the result of gregarious settlement of larvae in response to cues associated with conspecific adults. In this study, we investigated the existence of larval metamorphic cues associated with adults of C. onyx, a slipper limpet introduced to Hong Kong from the U.S. in the 1970s, through a series of laboratory bioassays. The results showed that derived cues in adult C. onyx were waterborne and the waterborne cues were not derived from bacteria associated with the shell and soft body of the adult Crepidula. The natural biofilm also induced the larval metamorphosis of C. onyx. The cues from the biofilm were associated with the surface of the biofilm and were not waterborne. The aggregated distribution in nature of adult C. onyx may result from a selective larval settlement process. On a small scale in the water column near the conspecific adults, larvae of C. onyx initially detect the waterborne conspecific cues, which then lead to positive downward swimming or passive sinking. This activity increases the chances for larvae to make contact with the biofilm and to be exposed into the higher concentration of waterborne conspecific cues. This may eventually lead to the enhanced larval settlement pattern on or near the conspecific adults.     

Impact of snowdrop lectin (Galanthus nivalis agglutinin; GNA) on adults of the green lacewing, Chrysoperla carnea

Based on the finding that Galanthus nivalis agglutinin (GNA) has direct negative effects on larvae of Chrysoperla carnea, laboratory experiments were conducted to investigate its toxicity to the adults. While the ingestion of GNA dissolved in an artificial diet did not affect adult longevity, there were concentration-dependent negative effects on the pre-oviposition period, daily fecundity and total fecundity (number of eggs laid). When GNA was ingested by larvae of C. carnea, it caused a significant extension of larval development time. Adults that had emerged from GNA-fed larvae did not differ from those that developed from control larvae in terms of adult fresh weight, pre-oviposition period and daily or total fecundity. However, fertility (proportion of hatching eggs) was significantly decreased in adults raised from GNA-treated larvae. Western blots revealed that GNA ingested by larvae of C. carnea was partly transferred to the adult stage and was subsequently excreted or digested within a few days. Our toxicity studies (Tier-1 tests) clearly established a hazard of GNA to adult C. carnea when administered to larvae or adults at high concentrations. Implications of these toxicity data for the non-target risk assessment of GNA-expressing transgenic crops are discussed.     

The importance of life-history stage and individual variation in the allorecognition system of a marine sponge

In marine invertebrates with complex life cycles, it may often be the case that trade-offs and behaviors differ between adult and larval stages. In this study, I examined the effects of life-history stage on allorecognition system function in the sponge, Haliclona sp. For sedentary marine invertebrates, allorecognition systems allow individuals to distinguish between genetically similar and distinct tissue they may encounter and are thought to reduce costly tissue fusion with individuals other than self or kin. Although it was found that sessile adults fused preferentially with self-tissue and exhibited a functioning allorecognition system, free-swimming larvae fused equally with sibling and non-sibling larvae resulting in swimming chimeras capable of successful metamorphosis, suggesting a stage-activated allorecognition system. In addition, adult sponges differed significantly in the propensity of their larvae to fuse suggesting variation in parental strategies. Analysis of larval swimming behavior indicated that larvae aggregate and are capable of increasing their encounters with other larvae and perhaps their probability of fusing in nature. The pursuit of fusion at this motile stage, along with evidence of a functioning adult allorecognition system, suggests that larvae may not express a recognition system, or that factors other than relatedness such as benefits to larval or adult chimeras, are involved in larval fusion and a stage-activated allorecognition system. In addition, this study demonstrates the presence of variation among individuals in the allorecognition system's ontogeny in the sponge Haliclona sp.     

The influence of starvation on mortality,development, and protein content in parasitized and unparasitized Tribolium castaneum

The effects of starvation on mortality, development, and protein content in Nosema whitei-infected and uninfected Tribolium castaneum were investigated. T. castaneum larvae, starved for 4, 6, 8, and 10 days postinfection, showed an increase in larval mortality. Pupal mortality also increased, producing a decrease in adult emergence. Starvation of larvae for 6 days or more delayed development and the average time to adult emergence increased. These effects tended to be more marked in Nosema-infected larvae. No consistent pattern of weight changes was observed in either the uninfected or infected pupae and adults. Infected T. castaneum larvae showed a significant decrease in protein compared to controls. Starvation apparently does not aggravate this condition nor does it have any significant effects on the total hemolymph protein content of uninfected and infected larvae.     

The energetic costs of case construction in the caddisfly Limnephilus rhombicus: direct impacts on larvae and delayed impacts on adults

Caddisflies, whose aquatic larvae build a portable case with silk, are a suitable model organism to test the impacts of resource allocation trade-off during development and examine the evolution of life-history strategies. In the caddisfly Limnephilus rhombicus, adult feeding is minimal. Therefore, the whole resources are acquired during the larval phase and must be allocated to case construction, growth and reproduction. In this study, the larval energetic reserves of L. rhombicus were manipulated by forcing larvae to rebuild their cases in the final larval stage. This allowed us to measure the physiological cost of construction. First, we recorded oxygen consumption during case reconstruction. Second, we measured the sugar, protein and lipid contents of larvae forced to rebuild their case and of larvae required only to re-enter on their case. Larvae had their sugar, protein and lipid content measured after the rebuilding event and 72 h later. The same analyses were carried out with adults immediately after emergence. We found that larvae forced to rebuild a case consumed 1.5 times more oxygen than control larvae. This energy expenditure generated a cost that was estimated to be a loss of larval protein of approximately 35%. Insects were unable to compensate for this loss of proteins during the end of the larval stage, and their metamorphosis to adults was also impacted. Therefore, we suggest that loss of larval protein is linked to silk production and may alter fitness.     

Pyrokinin/PBAN-like peptides in the central nervous system of mosquitoes

The pyrokinin/pheromone biosynthesis activating neuropeptide (PBAN) family of peptides is characterized by a common C-terminal pentapeptide, FXPRLamide, which is required for diverse physiological functions in various insects. Polyclonal antisera against the C-terminus was utilized to determine the location of cell bodies and axons in the central nervous systems of larval and adult mosquitoes. Immunoreactive material was detected in three groups of neurons in the subesophageal ganglion of larvae and adults. The corpora cardiaca of both larvae and adults contained immunoreactivity indicating potential release into circulation. The adult and larval brains had at least one pair of immunoreactive neurons in the protocerebrum with the adult brain having additional immunoreactive neurons in the dorsal medial part of the protocerebrum. The ventral ganglia of both larvae and adults each contained one pair of neurons that sent their axons to a perisympathetic organ associated with each abdominal ganglion. These results indicate that the mosquito nervous system contains pyrokinin/PBAN-like peptides and that these peptides could be released into the hemolymph. The peptides in insects and mosquitoes are produced by two genes, capa and pk/pban. Utilizing PCR protocols, we demonstrate that products of the capa gene could be produced in the abdominal ventral ganglia and the products of the pk/pban gene could be produced in the subesophageal ganglion. Two receptors for pyrokinin peptides were differentially localized to various tissues.     

Evidence for brain-derived neurotrophic factor-like neuropeptide in brain of the silk moth Bombyx mori during postembryonic periods

Brain-derived neurotrophic factor-like neuropeptide is produced in the brain of the silk moth, Bombyx mori. Immunocytochemical studies of brain and retrocerebral complex of larvae, prepupae, pupae and adults showed that four pairs of median neurosecretory cells and six pairs of lateral neurosecretory cells which had different immunoreactivities to BDNF peptide. Day-1 adult brains showed no evidence of neurons stained by anti-BDNF antibodies. Those reactivities, which were much stronger in median cells than in lateral cells, were the weakest in an earliest larval stage and a latest pupal stage but the strongest in late larval stage. Median neurosecretory cells projected their axons into the contralateral corpora allata by decussation in the median region, nerve corpora cardiaca (NCC) I, and nerve corpora allata (NCA) I, whereas lateral neurosecretory cells extended their axons to the ipsilateral corpora allata via NCC II and NCA I.     

What does not kill them makes them stronger: larval environment and infectious dose alter mosquito potential to transmit filarial worms

For organisms with complex life cycles, larval environments can modify adult phenotypes. For mosquitoes and other vectors, when physiological impacts of stressors acting on larvae carry over into the adult stage they may interact with infectious dose of a vector-borne pathogen, producing a range of phenotypes for vector potential. Investigation of impacts of a common source of stress, larval crowding and intraspecific competition, on adult vector interactions with pathogens may increase our understanding of the dynamics of pathogen transmission by mosquito vectors. Using Aedes aegypti and the nematode parasite Brugia pahangi, we demonstrate dose dependency of fitness effects of B. pahangi infection on the mosquito, as well as interactions between competitive stress among larvae and infectious dose for resulting adults that affect the physiological and functional ability of mosquitoes to act as vectors. Contrary to results from studies on mosquito–arbovirus interactions, our results suggest that adults from crowded larvae may limit infection better than do adults from uncrowded controls, and that mosquitoes from high-quality larval environments are more physiologically and functionally capable vectors of B. pahangi. Our results provide another example of how the larval environment can have profound effects on vector potential of resulting adults.     

Specificity of accumulation and transmission of tomato spotted wilt virus (TSWV) in two genera, Frankliniella and Thrips (Thysanoptera: Thripidae)

The accumulation and transmission of tomato spotted wilt virus (TSWV) was examined in second instar larvae and adults of two thrips genera, Frankliniella and Thrips. The species tested were F. occidentalis (Pergande), F. intonsa (Trybom), T. tabaciLindeman, T. setosus Moulton, T. palmi Karny and T. hawaiiensis (Morgan). In a standard petunia leaf disc assay, the efficiencies of TSWV transmission by two species of Frankliniella were higher than those of any Thrips species in the adult stage. A triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) showed that large amounts of the TSWV-nucleocapsid (N) protein were present in the ELISA-positive larvae of each species, with the exception of T. palmi. The ELISA titre of and the proportion of virus-infected individuals of the two Frankliniella species increased or did not significantly change from the larval to the adult stages, whereas those of the four Thrips species decreased significantly. These results show that the specificity of virus transmission by adult thrips is probably affected by the amount of viral N protein accumulation in the adults and that the accumulation pattern from the larval to the adult stages is in between the two genera tested in the present study.     

Ommochrome synthesis and kynurenic acid excretion in relation to metamorphosis and allatectomy in the stick insect, Carausius morosus Br.

End products of tryptophan metabolism in Carausius morosus are the ommochromes ommin and xanthommatin in the epidermis, and kynurenic acid in the faeces. During larval and adult life ommochromes and mainly kynurenic acid are formed. The concentration of kynurenic acid in the faeces of adult females is 2.5 times lower than in the larvae and in adult males. Allatectomy on the first day after a larval moult induces a much longer instar (10 days) than normal. After the following moult, the allatectomized animals are transformed into adultoids. The allatectomized and normal larvae produce similar amounts of kynurenic acid and ommochrome during the larval instar. Twenty days after last ecdysis, the ommochrome content in adult and adultoids is increased. In the faeces of adultoids, however, the concentration of kynurenic acid is higher than in normal female adults, but lower than in males and larvae.     

Influence of Dietary Experience on the Induction of Preference of Adult Moths and Larvae for a New Olfactory Cue

In Lepidoptera, host plant selection is first conditioned by oviposition site preference of adult females followed by feeding site preference of larvae. Dietary experience to plant volatile cues can induce larval and adult host plant preference. We investigated how the parent’s and self-experience induce host preference in adult females and larvae of three lepidopteran stem borer species with different host plant ranges, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and the monophagous Busseola nairobica, and whether this induction can be linked to a neurophysiological phenotypic plasticity. The three species were conditioned to artificial diet enriched with vanillin from the neonate larvae to the adult stage during two generations. Thereafter, two-choice tests on both larvae and adults using a Y-tube olfactometer and electrophysiological (electroantennography [EAG] recordings) experiments on adults were carried out. In the polyphagous species, the induction of preference for a new olfactory cue (vanillin) by females and 3^rd instar larvae was determined by parents’ and self-experiences, without any modification of the sensitivity of the females antennae. No preference induction was found in the oligophagous and monophagous species. Our results suggest that lepidopteran stem borers may acquire preferences for new olfactory cues from the larval to the adult stage as described by Hopkins’ host selection principle (HHSP), neo-Hopkins’ principle, and the concept of ‘chemical legacy.’     

Nosema ceranae Can Infect Honey Bee Larvae and Reduces Subsequent Adult Longevity

Nosema ceranae causes a widespread disease that reduces honey bee health but is only thought to infect adult honey bees, not larvae, a critical life stage. We reared honey bee (Apis mellifera) larvae in vitro and provide the first demonstration that N. ceranae can infect larvae and decrease subsequent adult longevity. We exposed three-day-old larvae to a single dose of 40,000 (40K), 10,000 (10K), zero (control), or 40K autoclaved (control) N. ceranae spores in larval food. Spores developed intracellularly in midgut cells at the pre-pupal stage (8 days after egg hatching) of 41% of bees exposed as larvae. We counted the number of N. ceranae spores in dissected bee midguts of pre-pupae and, in a separate group, upon adult death. Pre-pupae exposed to the 10K or 40K spore treatments as larvae had significantly elevated spore counts as compared to controls. Adults exposed as larvae had significantly elevated spore counts as compared to controls. Larval spore exposure decreased longevity: a 40K treatment decreased the age by which 75% of adult bees died by 28%. Unexpectedly, the low dose (10K) led to significantly greater infection (1.3 fold more spores and 1.5 fold more infected bees) than the high dose (40K) upon adult death. Differential immune activation may be involved if the higher dose triggered a stronger larval immune response that resulted in fewer adult spores but imposed a cost, reducing lifespan. The impact of N. ceranae on honey bee larval development and the larvae of naturally infected colonies therefore deserve further study.     

The development and function of the female germ line in Drosophila melanogaster: a cell lineage study.

X-ray-induced mitotic recombination was used to follow the development and function of the female germ line in Drosophila melanogaster. Clones marked by maternal effect mutations which alter the morphology of the egg [fs(1)K10] or the phenotype of the resulting progeny (maroonlike) were produced in trans-heterozygotes irradiated during embryonic, larval, or pupal development or as 5-day-old adults. Judging from the size of clones induced at the blastoderm stage, only five to ten of the pole cells observed on the surface of the embryo contribute to the germ line. Most of the K10 clones induced during embryonic and larval development were associated with mal twin spots, indicating that both daughters of the irradiated germ cell remained in the germ line and gave rise to eggs in the adult. During larval life the number of cells increases logarithmically and reaches a maximum of 110 at 24 hr after pupation. The same value was obtained for 5-day-old adults. In contrast to the mosaic females produced as embryos and larvae, mosaics obtained after pupal and adult irradiations were of two types, those laying only one K10 egg and those laying several K10 eggs distributed over the lifespan of the adult. This result indicates that the stem cell divisions characteristic of the adult period have begun shortly after pupation. About 9 to 11 days are required for an irradiated stem cell to produce its first clonal K10 egg, and two-thirds of this time is spent in the germarium. Each ovariole possesses on the average two to three functioning stem cells. This multiplicity of stem cells was confirmed by the recovery of mosaic ovarioles when mal heterozygotes irradiated as adults or late larvae were stained for aldehyde oxidase activity.